1. BASIC PROFESSIONAL TRAINING COURSE Module V Safety classification of structures, systems and components Case Studies
Version 1.0, May 2015
This material was prepared by the IAEA and co-funded by the European Union. 

2. Introduction
Students should be divided into groups by countries which they represent – presuming it is an international course.
If it is a national course, students should be divided into groups. If possible, regulators, operators and representatives from the industry should be in mixed groups to make the maximize exchange of information between them. Also it is a learning opportunity for them to have a different perspectives.
All the groups will participate in addressing the topic and prepare a short presentation for the plenary session.

3. Instructions
Task: Each group should analyse a flow chart indicating the safety classification process and prepare examples in the safety classification process.
The goal is to understand the Safety Classification process according to new safety guide SSG-30.
Each group should use the IAEA Specific Safety Guide No. SSG- 30.
Each group should prepare a short report for a plenary session.

4. The safety classification process
START
Basic understanding of the plant design, its safety analysis and how the main safety functions will be achieved
Identification of all functions
necessary to fulfil the main safety functions in all plant states, including modes of normal operation (see para. 3.3)
Identification of design provisions necessary to prevent accidents, to limit the effects of hazards or to protect workers, the public and the environment against radiological risks in operational conditions
(see paras. 3.8 and 3.9)
Categorization of the functions
(see para in Section 3)
Identification and classification of the SSCs performing the categorized functions
(see para in Section 3)
Identification and classification of the SSCs implemented as design provisions
(see para in Section 3)
Is the classification correct and complete? NO
YES
SELECTION OF APPLICABLE ENGINEERING DESIGN RULES FOR
STRUCTURES, SYSTEMS AND COMPONENTS (See section 4)

5. Identification of functions to be categorized
The functions to be categorized are those required to achieve the main safety functions for the different plant states, including all modes of normal operation.
TASK: Give examples of functions to be accomplished in different plant states.

6. Identification of design provisions
The safety of the plant is dependent on the reliability of different types of features, some of which are designed specifically for use in normal operation.
According to Safety guide SSG-30, these SSCs are termed ‘design provisions’.
TASK: Give the examples of design provisions.

7. Scope/ Design provisions
Design provisions contribute to the accomplishment of the main safety functions in operational conditions and accident conditions. Design provisions are mainly implemented for the following reasons:
To protect people (workers and the public) and the environment from harmful effects of radiation (direct radiation, airborne activity and releases of radioactive material);
To prevent the failure of an SSC not considered in the design basis for the plant (e.g. rupture of the reactor pressure vessel for LWR;
To reduce the frequency of failure of SSCs that may cause an accident;
To limit the effects of hazards considered in the design basis for the plant;
To prevent a postulated initiating event from developing into a more serious sequence without the occurrence of another independent failure.

8. Categorization of functions
The categorization of functions recommended in Safety Guide SSG- 30 is based on the following three safety categories:
Safety category 1;
Safety category 2;
Safety category 3.
TASK:
Give examples for each safety category.
Justify the category for each example.

9. Reflected by the PIE category: AOO, DBA, DEC
Scope/ Functions
Functions required to achieve the main safety functions for the different plant states, including modes of normal operation (credited in the safety analysis).
Functions are categorized on the basis of their safety significance:
Consequences of failure to perform the function;
Frequency of occurrence of the postulated initiating event for which the function will be called upon;
Time following a postulated initiating event at which, or the period of time during which, the function will be required to be performed.
e.g. High, Medium and low
Reflected by the PIE category: AOO, DBA, DEC

10. Classification of structures, systems and components
Once the safety categorization of the functions is completed, for each safety function, all the systems necessary to perform a single safety functions should be identified.
Systems and then SSCs performing these functions should be assigned to a safety class:
Safety class 1;
Safety class 2;
Safety class 3.
TASK: Give examples of SSCs performing categorized functions (systems and individual components).
Determine the right safety class;
Justify the safety class for each example;
Explain how the confinement barrier role of individual SSCs influence the safety class.

11. Classification of structures, systems and components (SSC as “design provision”)
SSC implemented as a design provision can be classified directly by assessing the level of severity of its failure.
Safety class 1;
Safety class 2;
Safety class 3.
TASK:
Give examples of SSCs designed as “design provision”;
Determine the right safety class;
Justify the safety class for each example.
The views expressed in this document do not necessarily reflect the views of the European Commission.